<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <script>
        var msg;
        console.log(msg == undefined) // true
        console.log(null == undefined)  // true

        console.log(1.0)
        console.log(5/2)

        //	parseInt()
        //	parseFloat()

        console.log(parseFloat("2.2")+1)
        //isNaN 是不是非数字
        console.log(isNaN("a"));    // true
        console.log('I\'m \"OK\"!')

        console.log( '\x41\x42')
        console.log('\u4e2d\u6587')
        console.log(`
            测试
            多行内容

        尝试写点格式。
        ！
        `)
        console.log( "3.0" === 3.0)
        console.log( "3.0" == 3.0)
    </script>
</body>
</html>